Rapid fabricating technique for multi-layered human hepatic cell sheets by forceful contraction of the fibroblast monolayer

Abstract

Cell sheet engineering is attracting attention from investigators in various fields, from basic research scientists to clinicians focused on regenerative medicine. However, hepatocytes have a limited proliferation potential in vitro, and it generally takes a several days to form a sheet morphology and multi-layered sheets. We herein report our rapid and efficient technique for generating multi-layered human hepatic cell (HepaRG® cell) sheets using pre-cultured fibroblast monolayers derived from human skin (TIG-118 cells) as a feeder layer on a temperature-responsive culture dish. Multi-layered TIG-118/HepaRG cell sheets with a thick morphology were harvested on day 4 of culturing HepaRG cells by forceful contraction of the TIG-118 cells, and the resulting sheet could be easily handled. In addition, the human albumin and alpha 1-antitrypsin synthesis activities of TIG-118/HepaRG cells were approximately 1.2 and 1.3 times higher than those of HepaRG cells, respectively. Therefore, this technique is considered to be a promising modality for rapidly fabricating multi-layered human hepatocyte sheets from cells with limited proliferation potential, and the engineered cell sheet could be used for cell transplantation with highly specific functions.

Figure 1. Schematic diagrams of the fabrication process used for the human hepatic cell (HepaRG) sheets.

The processes used to fabricate the HepaRG cell-only sheet (A) and TIG-118/HepaRG cell sheet (B).

Figure 2. Cell morphologies of HepaRG cells and TIG-118/HepaRG cells on TRCD.

Phase-contrast (A–D) and fluorescent (E, F) micrographs of the HepaRG cells (A, B) and TIG-118/HepaRG cells (C–F) on a TRCD. After one day (A, C, E) and three days (B, D, F) of culturing HepaRG cells. Green (CellTracker Green CMFDA): TIG-118 cells, Red (CellTracker Orange CMRA): HepaRG cells. The bars represent 200 µm (A–D) and 50 µm (E, F).

Figure 3. Cell distributions of TIG-118/HepaRG cells on TRCD.

Cross-section views (A, B) and the cell population (C, D) of the TIG-118/HepaRG cells. After one day (A, C) and three days (B, D) of culturing HepaRG cells. The bars represent 50 µm.

Figure 4. Cell morphologies of HepaRG cell and TIG-118/HepaRG cell sheets.

Exterior photographs (above) and phase-contrast micrographs (below) after incubation at 20°C. (A, B) HepaRG cells and (C, D) TIG-118/HepaRG cells. After one day (24 hours) (A, C) and four days (B, D) of culturing HepaRG cells. The bars represent 100 µm.

Figure 5. Cell distributions and HE stained images of the cross-sections of cell sheets.

Fluorescent (A, B) and HE (C–F) stained images. (A, C) HepaRG cells, (B, D, E) TIG-118/HepaRG cells and (F) TIG-118 cells. Green (CellTracker Green CMFDA): TIG-118 cells, Red (Alexa Fluor 568 Phalloidin): F-actin, Blue (DAPI): nucleus. The bars represent 50 µm.

Figure 6. Ultrastructures of the TIG-118/HepaRG cell sheets observed by TEM.

(A) Low magnification and (B–D) high magnification images of the cell-cell adhesion between HepaRG cell and TIG-118 cell (B), HepaRG cells (C) and TIG-118 cells (D). HR, HepaRG cell; TIG, TIG-118 cell; N, nucleus; BC, bile canaliculi; TG, tight junctions; GJ, gap junctions. The bars represent 5 µm (A) and 500 nm (B–D).

Figure 7. Characteristics of cell sheets.

Diameters (A) and thicknesses (B) of cell sheets. The dashed line indicates the diameter of a TRCD.

Figure 8. Live and dead stained fluorescent images.

(A–C) HepaRG cells and (D–F) TIG-118/HepaRG cells. (A, D) After four days of culturing HepaRG cells on the TRCD and (B, E) after two hours and (C, F) 24 hours of reculturing cell sheets on glass-based dishes. Green (Calcein-AM): viable cells, red (PI): dead cells. The bar represents 200 µm.

Figure 9. Liver-specific functions of HepaRG cells and TIG-118/HepaRG cells on TRCD.

Human albumin (A) and A1AT (B) synthesis rates.